Photographic materials generally comprise a support which has electrically insulating properties and a photographic layer. In many cases electrostatic charges build up as a result of contact friction with, or separation from, the surface of a material of the same or a different type during the manufacture or use of the photographic material. The accumulated electrostatic charge causes a lot of damage, but most importantly spots or dendritic or feather-like lines appear when the photographic film is developed when of the light-sensitive emulsion layer is exposed as a result of the discharge of the accumulated electrostatic charge prior to development processing. These types of marks are usually referred to as static marks, and the commercial value of the photographic film can be reduced to a considerable degree and, depending on the particular case, it may be lost completely.
The accumulated electrostatic charge may also cause dust to be become attached to the surface of the film, and it may give rise to other secondary problems such as preventing a uniform coating.
Such electrostatic charges are generated as a result of contact with and separation from mechanical parts during the manufacture of the photographic material, as mentioned earlier, or in various types of automatic camera devices. Static mark formation has increased recently because of the increased photographic speeds of photographic materials and as a result of the more vigorous handling of the material during high speed coating, high speed camera operation and high speed automatic development processing. Moreover, the attachment of dust has become a problem when processed films are handled.
The addition of an antistatic agent to a photographic material is desirable to prevent the occurrence of such problems due to static electricity. However, antistatic agents which are used generally in other fields cannot be used without changing the photographic materials. Various limitations exist when antistatic agents are used photographic materials. In addition to excellent antistatic performance, the antistatic agents used in photographic materials must not adversely affect the photographic characteristics, such as photographic speed, fog level, graininess and sharpness, of the material, must not adversely affect the film strength of the material and must not adversely affect antistick properties. Also they must not increase the rate at which the development bath for the photographic material becomes fatigued, they must not contaminateautomatic developing machine transporting rollers and they must not reduce the strength of adhesion between the various structural layers of the photographic material. A large number of limitations are thus imposed on the use of antistatic agents in photographic materials.
One way of minimizing the problems due to static electricity is to increase the electrical conductivity of the surface of the photographic material so that the electrostatic charge is dispersed quickly before an accumulated charge can discharge. This is especially effective in terms of the attachment of dust after processing.
Hence, methods of increasing the electrical conductivity of the support and the various coated surface layers of a photographic material have been considered in the past. Attempts have been made to use various hygroscopic substances and water soluble substances, and certain types of surfactants and polymers, for example.
However, these substances may be specific to the type of film support and differences in photographic composition, and the electrical conductivity may be lost after processing and dust may become attached to the film. Moreover, there may be a humidity dependence and static charges may build up under low humidity conditions, there may be an adverse effect on photographic performance, coating properties or transparency, there may be a deterioration in adhesion, or contamination of the development processing baths may occur. Thus, it is very difficult to use these materials in photographic materials.